The present invention relates to a seat carrier for chairs, particularly suitable for use in swivel office chairs.
European Patent No. 0198056 describes a seat carrier for chairs, especially for swivel office chairs. This carrier is described as comprising a U-shaped base structure containing legs pointed in an upward direction. At one end of the carrier there is a receptacle for a central support leg, a T-shaped seat plate carrier with lateral tabs directed in a downward direction. The seat plate carrier at its front end, i.e., the end closest to the cross member of the T, is pivotally connected with the base structure (at the end of the base structure which is opposite the receptacle) about a first arbor mounted to the legs of the base structure and the tabs of the seat carrier. The base structure extends from the connection with the seat plate carrier diagonally downward and in a rear direction.
The seat carrier further comprises a U-shaped back rest carrier whose legs point in a downward direction and which is pivotally-connected with the seat plate carrier, at the seat plate carrier's rear end, about a second arbor mounted in the tabs of the seat plate carrier and in a middle sector of the legs of the back rest carrier. A third arbor is mounted in matching holes in the legs of the base structure approximately in the middle of the connection with the seat plate and the receptacle for the supporting leg and in slots directed in a forward and a downward direction at the front end of the back rest carrier, and the tabs of the seat platform carrier at least partially encompass the legs of the back rest carrier, and the legs of the back rest carrier at least encompass the legs of the base structure.
Between the seat platform carrier and the base structure there are one more spring elements arranged in such a manner as to push these apart. Also, between the tabs of the seat platform carrier and the legs of back rest carrier are arranged two intermeshing lamellar stacks. One set of lamellar stacks at one end contains slots which are directed toward the slots of the back rest carrier in which the third arbor is guided and its other end its other end is pivotally mounted to bolts in the legs of the back rest carrier, while the other set of lamellar stacks contains at the end directed towards the slots of the back rest carrier contains slots in which the third arbour is guided and its other end is pivotally mounted to bolts in the tabs of the seat platform carrier. Coaxially to the third arbour chucking means connect the back rest carrier and the base structure.
However, the seat carrier of the prior art has several disadvantages in that under stress the individual parts can shift their position in relation to each other a way that the activation of the chucking means is no longer satisfactory, i.e., the lamellar stacks either become jammed to the legs of the base structure and the back rest carrier and are difficult to release, or they fail to lock sufficiently.